JP2015232589A - Intermediate transfer belt and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt that suppresses unevenness in the density of images and a change in the density of images due to a temperature and humidity environment, even when forming images on rough paper.SOLUTION: An intermediate transfer belt has a surface layer 12 formed on a base 11, and the surface layer 12 includes polyrotaxane and acidic carbon black, where the difference between the common logarithm value of the surface resistivity on a side where the surface layer 12 is formed at 10°C and 15%RH and the common logarithm value of the surface resistivity on the side where the surface layer 12 is formed at 27°C and 80%RH is 2[Log(Ω/sq.)] or less.

Description

  The present invention relates to an intermediate transfer belt and an image forming apparatus.

  Conventionally, in an electrophotographic image forming apparatus, a developed image of four colors of yellow, magenta, cyan, and black is once superimposed on an intermediate transfer belt, and then transferred to a recording medium such as paper at once. It is used.

  In recent years, rough paper such as recycled paper, embossed paper, Japanese paper, kraft paper, and the like is increasingly used as a recording medium. Such followability to rough paper is important. If the followability is poor, unevenness in image density due to unevenness of the rough paper occurs.

  Patent Document 1 discloses an image forming apparatus belt containing a polyrotaxane and / or a crosslinked polyrotaxane as an image forming apparatus belt used in an image forming apparatus that forms an image by electrophotography.

  However, even when an image is formed on rough paper, it is desired to reduce the variation in image density due to uneven image density and temperature / humidity environment.

  In view of the above-described problems of the related art, an object of one embodiment of the present invention is to provide an intermediate transfer belt in which even when an image is formed on rough paper, variation in image density and change in image density due to a temperature and humidity environment are small. And

  One aspect of the present invention is an intermediate transfer belt in which a surface layer is formed on a substrate, and the surface layer includes polyrotaxane and acidic carbon black, and the surface layer is formed at 10 ° C. and 15% RH. The difference between the common logarithm of the surface resistivity and the common logarithm of the surface resistivity on the side where the surface layer is formed at 27 ° C. and 80% RH is 2 [Log (Ω / □)] or less.

  According to one embodiment of the present invention, it is possible to provide an intermediate transfer belt in which even when an image is formed on rough paper, an image density unevenness and a change in image density due to a temperature and humidity environment are small.

FIG. 3 is a cross-sectional view illustrating an example of a structure of an intermediate transfer belt. 1 is a schematic diagram illustrating an example of an image forming apparatus. It is a schematic diagram which shows the other example of an image forming apparatus.

  Next, the form for implementing this invention is demonstrated with drawing.

  FIG. 1 shows an example of the structure of the intermediate transfer belt.

  In the intermediate transfer belt, a flexible surface layer 12 is formed on a base 11 having a relatively high rigidity for obtaining a relatively flexible property.

The surface resistivity of the intermediate transfer belt on the side where the surface layer 12 is formed at 10 ° C. and 15% RH and the surface resistivity on the side where the surface layer 12 is formed at 27 ° C. and 80% RH are respectively _{expressed as} R _LL [Ω / □] and R _HH [Ω / □], the formula LogR _LL -LogR _HH ≦ 2
Meet. When LogR _LL -LogR _HH exceeds 2 [Log (Ω / □)], the change in image density due to the temperature and humidity environment increases. Note that LogR _LL -LogR _HH is usually 3 [Log (Ω / □)] or more.

The surface resistivity on the side where the surface layer 12 is formed at 23 ° C. and 50% RH of the intermediate transfer belt is usually 1 × 10 ⁸ to 1 × 10 ¹³ Ω / □.

The volume resistivity on the side on which the surface layer 12 is formed at 23 ° C. and 50% RH of the intermediate transfer belt is usually 1 × 10 ⁸ to 1 × 10 ¹¹ Ω · cm.

  The intermediate transfer belt may have a seam, but is preferably a seamless belt. Thereby, durability and image quality can be improved.

  First, the substrate 11 will be described.

  In the base 11, an electric resistance adjusting agent for adjusting electric resistance is dispersed in the resin.

  Although it does not specifically limit as resin, Fluorine-type resin, such as PVDF and ETFE, a polyimide, a polyamideimide, etc. are mentioned. Among these, polyimide or polyamideimide is preferable from the viewpoint of mechanical strength (high elasticity) and heat resistance.

  Although it does not specifically limit as an electrical resistance modifier, A metal oxide, carbon black, an ionic conductive agent, a conductive polymer, etc. are mentioned, You may use 2 or more types together.

  Examples of the metal oxide include zinc oxide, tin oxide, titanium oxide, zirconium oxide, aluminum oxide, and silicon oxide.

  The metal oxide may be subjected to a surface treatment. Thereby, the dispersibility in resin can be improved.

  Examples of carbon black include ketjen black, furnace black, acetylene black, thermal black, and gas black.

  Examples of ionic conductive agents include tetraalkylammonium salts, trialkylbenzylammonium salts, alkylsulfonates, alkylbenzenesulfonates, alkyl sulfates, glycerol fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, and polyoxyethylene fatty alcohol esters. , Alkyl betaine, lithium perchlorate and the like.

  When carbon black is used as the electrical resistance adjusting agent, the content of carbon black in the substrate 11 is usually 10 to 25% by mass, and preferably 15 to 20% by mass. When the content of carbon black in the substrate 11 is 10% by mass or more, the uniformity of electrical resistance can be improved. On the other hand, when the content of carbon black in the substrate 11 is 25% by mass or less, the mechanical strength of the intermediate transfer belt can be improved.

  When a metal oxide is used as the electrical resistance adjuster, the content of the metal oxide in the substrate 11 is usually 1 to 50% by mass, and preferably 10 to 30% by mass. When the content of the metal oxide in the substrate 11 is 10% by mass or more, the uniformity of electrical resistance can be improved. On the other hand, when the content of the metal oxide in the substrate 11 is 25% by mass or less, the mechanical strength of the intermediate transfer belt can be improved.

  The substrate 11 may further include a dispersion aid, a reinforcing agent, a lubricant, a heat conductive agent, an antioxidant, and the like.

  The thickness of the substrate 11 is usually 30 to 150 μm, preferably 40 to 120 μm, and more preferably 50 to 80 μm. When the thickness of the base 11 is 30 μm or more, it is possible to suppress the belt from being split due to a crack. On the other hand, when the thickness of the base 11 is 150 μm or less, the belt can be prevented from cracking due to bending.

  The substrate 11 can be formed by applying a coating solution in which a resin or a resin precursor and an electrical resistance adjusting agent are dissolved or dispersed in an organic solvent and then drying the coating solution.

  Although it does not specifically limit as an organic solvent, N-methyl- 2-pyrrolidone etc. are mentioned, You may use 2 or more types together. Among these, N-methyl-2-pyrrolidone is preferable in that polyamic acid and polyamideimide, which are polyimide precursors, are easily dissolved.

  The method for applying the coating liquid is not particularly limited, and examples thereof include a spiral coating method, a die coating method, and a roll coating method.

  Next, the surface layer 12 will be described.

  The surface layer 12 includes polyrotaxane and acidic carbon black.

  Here, in the rotaxane, rod-shaped molecules having blocking groups at both ends are included by a cyclic molecule. The blocking group is a bulky group that can prevent the elimination of the cyclic molecule. A rod-like molecule having a blocking group at both ends penetrates a cyclic molecule and is not fixed to the cyclic molecule by a covalent bond. For this reason, the rod-like molecule can move freely in the cyclic molecule, and the cyclic molecule can also move along the rod-like molecule. That is, when stress is applied, the cyclic molecules can move freely along the rod-like molecules like a pulley. As a result, the surface layer 12 is excellent in stretchability and flexibility, and the followability to the recording medium is improved. Therefore, even when an image is formed on rough paper, the unevenness in image density is reduced.

  In polyrotaxane, rod-shaped molecules having blocking groups at both ends are included by a plurality of cyclic molecules.

  The rod-like molecule and / or the cyclic molecule may be modified with a hydrophobic group. Thereby, the solubility with respect to the organic solvent of a polyrotaxane can be improved.

  Although it does not specifically limit as a hydrophobic group, An alkyl group, a benzyl group, etc. are mentioned.

  Although it does not specifically limit as a rod-shaped molecule | numerator, Polyethylene glycol etc. are mentioned.

  The blocking group is not particularly limited, and examples thereof include an adamantyl group.

  The molecular weight of the rod-like molecules having blocking groups at both ends is usually 1000 to 50000, preferably 10,000 to 40000, and more preferably 20000 to 35000. When the molecular weight of the rod-like molecules having blocking groups at both ends is 1000 or more, it is possible to suppress a decrease in flexibility of the surface layer 12 and to improve scratch resistance and followability to the recording medium. On the other hand, when the molecular weight of the rod-like molecule having a blocking group at both ends is 50000 or less, an increase in the viscosity of the coating solution can be suppressed, and deterioration in appearance such as smoothness and gloss can be suppressed.

  In addition, the cyclic molecule does not necessarily need to be completely closed, and may be opened to such an extent that it does not desorb from the rod-like molecule.

  The cyclic molecule preferably has a reactive group in that it can be easily modified with a hydrophobic group.

  Although it does not specifically limit as a reactive group, A hydroxyl group, a carboxyl group, an amino group, etc. are mentioned. Among them, a hydroxyl group is preferable because it does not react with the blocking group when the blocking group is formed at both ends of the rod-like molecule.

  Although it does not specifically limit as a cyclic molecule, Cyclodextrins, crown ethers, etc. are mentioned, You may use 2 or more types together. Among these, cyclodextrins are preferable because they easily include rod-shaped molecules.

  Cyclodextrins are compounds in which a plurality of glucoses are cyclically bonded by α-1,4-glycoside bonds. Among them, compounds in which 6, 7, and 8 glucoses are bonded, that is, α-, β-, and γ-cyclodextrin are preferable, and α-cyclodextrin is more preferable from the viewpoint of inclusion.

  It is preferable that at least one of the hydroxyl groups of the cyclodextrins is modified with a hydrophobic group. Thereby, the solubility with respect to an organic solvent can be improved.

  The number of cyclic molecules that include rod-shaped molecules is not particularly limited.

  The polyrotaxane can be produced by a known method (for example, see Japanese Patent No. 437649).

  The polyrotaxane may be crosslinked with a crosslinking agent.

  Although it does not specifically limit as a crosslinking agent, Melamine resin, polyisocyanate (for example, hexamethylene diisocyanate, phenylene diisocyanate, diisocyanate tolylene), polyisocyanate with blocked isocyanate groups, cyanuric chloride, trimesoyl chloride, terephthaloyl Examples include chloride, epichlorohydrin, dibromobenzene, glutaraldehyde, divinylsulfone, 1,1′-carbonyldiimidazole, alkoxysilane, and the like, and two or more of them may be used in combination. Among these, a polyisocyanate is preferable from the viewpoint of easy crosslinking, and a polyisocyanate in which an isocyanate group is blocked is more preferable from the viewpoint of high storage stability at room temperature.

  Although it does not specifically limit as a blocking agent which blocks an isocyanate group, Oximes, diketones, phenols, caprolactams, etc. are mentioned.

  Examples of commercially available polyisocyanates include Duranate (manufactured by Asahi Kasei Chemicals Corporation), Takenate (manufactured by Mitsui Chemicals), Coronate (manufactured by Nippon Polyurethane Industry Co., Ltd.), Death Module (manufactured by Sumika Bayer Urethane Co., Ltd.), and the like.

  When the polyrotaxane has a hydroxyl group and a polyisocyanate is used as a crosslinking agent, the molar ratio of the isocyanate group to the hydroxyl group is usually 1.0 to 1.2. When the molar ratio of the isocyanate group to the hydroxyl group is 1.0 or more, the crosslinking proceeds sufficiently and the shape of the surface layer 12 can be maintained. On the other hand, when the molar ratio of the isocyanate group to the hydroxyl group is 1.2 or less, the flexibility of the surface layer 12 can be maintained.

  The temperature at which the polyrotaxane is crosslinked using a crosslinking agent is usually from 130 to 220 ° C, preferably from 140 to 200 ° C.

  The time for crosslinking the polyrotaxane using the crosslinking agent is usually 30 seconds to 5 hours.

  Although it does not specifically limit as a heating method at the time of bridge | crosslinking a polyrotaxane using a crosslinking agent, A press heating method, a steam heating method, an oven heating method, a hot air heating method etc. are mentioned.

  In addition, after cross-linking a polyrotaxane using a cross-linking agent, the polyrotaxane may be post-crosslinked in order to reliably cross-link to the inside.

  The time for post-crosslinking the polyrotaxane is usually 1 to 48 hours.

  The surface layer 12 may further contain a resin other than the polyrotaxane.

  Although it does not specifically limit as resin other than a polyrotaxane, An acrylic resin, a silicone resin, a fluororesin etc. are mentioned.

  Acidic carbon black can be synthesized by reacting neutral carbon black with nitrogen dioxide, ozone, nitric acid or the like.

  Although it does not specifically limit as a functional group which exists on the surface of acidic carbon black, A carboxyl group, a phenolic hydroxyl group, a quinone group, a lactone group etc. are mentioned.

  The pH of acidic carbon black is less than 7, preferably 5 or less, and more preferably 3.5 or less. For this reason, dispersibility with respect to the polyrotaxane is improved and variation in electric resistance is reduced. Therefore, even when an image is formed on rough paper, unevenness in image density is reduced. Even if an image is formed on rough paper, the change in image density due to the temperature and humidity environment is reduced. Although this reason is not certain, it is considered that acidic carbon black tends to exist on the surface of the surface layer 12. As a result, moisture absorption by the polyrotaxane can be suppressed.

  The pH of acidic carbon black is the pH of a mixed solution of carbon black and distilled water, and can be measured according to JIS K6221-1982.

  The volatile content of acidic carbon black is preferably 15% or less, and more preferably 5% or less. Thereby, since the change in the surface resistivity due to the temperature and humidity environment is further reduced, the change in the image density due to the temperature and humidity environment is further reduced.

  Note that the volatile content is a weight loss when acidic carbon black is heated at 950 ° C. for 7 minutes, and generally increases as the number of functional groups present on the surface increases.

  As commercial products of acidic carbon black, MA7, MA8, MA11, MA77, MA78, MA100, MA100R (manufactured by Mitsubishi Chemical Corporation), Special Black4, Special Black4A, Special Black5, Special Black V, Printex U, Printex U, Printex U 140U, Printex 140V, Color Black FW200, Color Black FW2, Color Black FW2V, Color Black FW1, Color Black FW18 (above, manufactured by Orion Engineered Carbons).

  The content of acidic carbon black in the surface layer 12 is usually 20% by mass or less, and preferably 15% by mass or less. As a result, the followability of the intermediate transfer belt to rough paper can be improved.

  The surface layer 12 may further contain a dispersant. Thereby, the dispersibility of acidic carbon black can further be improved.

  Commercially available dispersants include DISPERBYK-130, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-166, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK-180, DISPERBYK-82, 183, DISPERBYK-184, DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2096, DISPERBYK-2150, DISPERBYK-2155, and more Sol sparse 13240, Sol sparse 13650, Sol sparse 11200, Sol sparse 13940, Sol sparse 17000, Sol sparse 18000, Sol sparse 20000, Sol sparse 21000, Sol sparse 20000, Sol sparse 24000, Sol sparse 26000, Sol sparse 27000, Sol sparse 28000, Sol sparse 32000, Sol sparse 36000, Sol sparse 36000 Solsperse 41000, Solsperse 42000, Solsperse 43000, Solsperse 46000, Solsperse 54000, Solsperse 71000 (manufactured by Lubrizol Corporation), and the like.

  The surface layer 12 may further contain a reinforcing agent, a lubricant, a heat conductive agent, an antioxidant, and the like.

  The surface layer 12 can be formed by applying a coating solution in which polyrotaxane and acidic carbon black are dissolved or dispersed in an organic solvent and then drying the coating solution.

  Although it does not specifically limit as an organic solvent, A cyclohexanone, methyl ethyl ketone, ethyl acetate, acetone, toluene, xylene, tetrahydrofuran etc. are mentioned, You may use 2 or more types together. Among these, cyclohexanone is preferable because polyrotaxane is easily dissolved and carbon black is easily dispersed.

  The disperser used when dispersing the acidic carbon black in the organic solvent is not particularly limited, and examples thereof include a bead mill, a sand mill, a nanomizer, and a ball mill.

  The method for applying the coating liquid is not particularly limited, and examples thereof include a spiral coating method, a die coating method, a roll coating method, and a spray coating method.

  The thickness of the surface layer 12 is usually 30 to 300 μm, and preferably 50 to 200 μm. When the thickness of the surface layer 12 is 30 μm or more, unevenness in image density when an image is formed on rough paper can be further reduced. On the other hand, when the thickness of the surface layer 12 is 300 μm or less, the intermediate transfer belt is easily bent, the warpage is increased and the running performance becomes unstable, or the belt is bent at the curvature portion of the roller supporting the intermediate transfer belt. It can suppress that a crack generate | occur | produces by doing.

  In the intermediate transfer belt, a relatively soft elastic layer containing rubber, elastomer or the like may be further formed between the base 11 and the surface layer 12. Thereby, the followability with respect to rough paper can be further improved.

  The intermediate transfer belt may further include an adhesive layer between the substrate 11 and the surface layer 12. Thereby, the adhesiveness of the base | substrate 11 and the surface layer 12 can further be improved.

  The image forming apparatus includes a photosensitive member, an intermediate transfer member, a charging unit that charges the photosensitive member, an exposure unit that exposes the charged photosensitive member to form an electrostatic latent image, and an electrostatic member formed on the photosensitive member. Developing means for developing the latent image with toner to form a toner image, first transfer means for transferring the toner image formed on the photosensitive member to the intermediate transfer member, and recording the toner image transferred to the intermediate transfer member Second transfer means for transferring to the medium is provided.

  The image forming apparatus may further include a static elimination unit, a cleaning unit, a recycling unit, a control unit, and the like.

  The image forming apparatus is preferably a full-color image forming apparatus in which image forming units of respective colors each having a photoconductor, a charging unit, an exposing unit, and a developing unit are arranged in series.

  FIG. 2 shows an example of the image forming apparatus.

  The primary transfer unit 500 includes an intermediate transfer belt 501 (see FIG. 1). Around the intermediate transfer belt 501, a secondary transfer bias roller 605 of the secondary transfer unit 600, a cleaning blade 504 for cleaning the intermediate transfer belt 501, and a lubricant application brush 505 for applying a lubricant are installed.

  A position detection mark (not shown) is provided on the outer peripheral surface or the inner peripheral surface of the intermediate transfer belt 501. However, when providing the position detection mark on the outer peripheral surface of the intermediate transfer belt 501, it is necessary to devise a way to avoid the passage area of the cleaning blade 504. The optical sensor 514 is provided between the primary transfer bias roller 507 and the drive roller 508 that detect the position detection mark and supports the intermediate transfer belt 501.

  The intermediate transfer belt 501 is supported by a primary transfer bias roller 507, a driving roller 508, a belt tension roller 509, a secondary transfer counter roller 510, a cleaning counter roller 511, and a feedback current detection roller 512.

  Each roller is made of a conductive material, and each roller other than the primary transfer bias roller 507 is grounded. The primary transfer bias roller 507 has a transfer bias controlled to a predetermined current or voltage by a primary transfer power source 801 that is controlled at a constant current or voltage according to the number of superimposed toner images. Is applied.

  The intermediate transfer belt 501 is driven in the direction of the arrow by a belt driving roller 508 that is driven to rotate in the direction of the arrow in the drawing by a drive motor (not shown).

  The intermediate transfer belt 501 is set to have a larger maximum size that can be passed through in order to superimpose toner images formed on the photosensitive drum 200.

  The secondary transfer bias roller 605 is configured to be able to contact and separate with respect to the outer peripheral surface of the intermediate transfer belt 501 supported by the secondary transfer counter roller 510 by a contact and separation mechanism described later. The secondary transfer bias roller 605 is installed so that the transfer paper P is sandwiched between the secondary transfer bias roller 605 and the intermediate transfer belt 501 supported by the secondary transfer counter roller 510, and the secondary transfer power source is controlled with constant current. By 802, a transfer bias having a predetermined current is applied.

  The registration roller 610 feeds the transfer paper P between the secondary transfer bias roller 605 and the intermediate transfer belt 501 supported by the secondary transfer counter roller 510 at a predetermined timing. The cleaning blade 608 is in contact with the secondary transfer bias roller 605. The cleaning blade 608 performs cleaning by removing the deposits attached to the surface of the secondary transfer bias roller 605.

  When the image forming operation is started, the photosensitive drum 200 is rotated in the direction of the arrow in the drawing by a drive motor (not shown), and a black (K) toner image and cyan (C) are formed on the photosensitive drum 200. A toner image, a magenta (M) toner image, and a yellow (Y) toner image are formed. The intermediate transfer belt 501 is rotated in the direction of the arrow in the drawing by the driving roller 508. As the intermediate transfer belt 501 rotates, the K toner image, C toner image, M toner image, and Y toner image are transferred by the transfer bias applied to the primary transfer bias roller 507. The toner images of the respective colors are superimposed on the intermediate transfer belt 501 in the order of C, M, and Y.

  For example, the K toner image is formed as follows.

  The charging charger 203 uniformly charges the surface of the photosensitive drum 200 to a predetermined potential with a negative charge by corona discharge. After the K image data is read by the color scanner at a predetermined timing based on the signal that has detected the position detection mark, the writing optical unit (not shown) is exposed to the laser beam based on the K image data. The As a result, in the exposed portion of the uniformly charged surface of the photosensitive drum 200, the electric charge proportional to the amount of the exposed light disappears, and a K electrostatic latent image is formed. When the negatively charged K toner adhering to the developing roller of the K developing device 231K comes into contact with the K electrostatic latent image, the K toner does not adhere to the remaining portion of the photosensitive drum 200. Then, K toner is adsorbed to a portion where no charge remains, that is, an exposed portion, and a K toner image is formed.

  The K toner image formed on the photosensitive drum 200 is transferred to the outer peripheral surface of the intermediate transfer belt 501 that is rotating at a constant speed while being in contact with the photosensitive drum 200.

  The K toner remaining on the surface of the photosensitive drum 200 after the transfer of the K toner image is cleaned by the cleaning device 201 and then uniformly discharged by the charge removal lamp 202.

  On the photosensitive drum 200, after the K toner image is formed, the C toner image is formed. Specifically, after the C image data is read by the color scanner at a predetermined timing, the writing optical unit (not shown) exposes with laser light based on the C image data. As a result, a C electrostatic latent image is formed on the surface of the photosensitive drum 200. Then, after the rear end portion of the K electrostatic latent image has passed and before the front end portion of the C electrostatic latent image arrives, the revolver developing unit 230 rotates, and the C developing unit 231C is set at the developing position. The C electrostatic latent image is developed with C toner to form a C toner image. Thereafter, similarly, an M toner image and a Y toner image are formed.

  The K toner image, C toner image, M toner image, and Y toner image sequentially formed on the photosensitive drum 200 are sequentially aligned and transferred onto the intermediate transfer belt 501. As a result, a toner image having a maximum of four colors superimposed on the intermediate transfer belt 501 is formed.

  On the other hand, when the image forming operation is started, the transfer paper P is fed from the transfer paper cassette or the manual feed tray, and is waiting at the nip of the registration roller 610.

  When the leading edge of the toner image on the intermediate transfer belt 501 approaches the nip formed by the intermediate transfer belt 501 supported by the secondary transfer counter roller 510 and the secondary transfer bias roller 605, the transfer paper P The registration roller 610 is driven so that the leading edge of the toner image coincides with the leading edge of the toner image, and the transfer paper P is conveyed along the transfer paper guide plate 601.

  In this way, when the transfer sheet P passes through the nip, the toner image on the intermediate transfer belt 501 is transferred onto the transfer sheet P by the transfer bias applied to the secondary transfer bias roller 605. The transfer paper P is transported along the transfer paper guide plate 601, neutralized by passing through a portion facing the neutralization charger 606, and then conveyed to the fixing device 270 by the belt conveyance device 210. Then, after the toner image is fixed at the nip between the fixing rollers 271 and 272 of the fixing device 270, the transfer paper P is sent out by a discharge roller (not shown) and stacked face up on a copy tray (not shown).

  Note that the fixing device 270 may include a belt component.

  Residual toner remaining on the outer peripheral surface of the intermediate transfer belt 501 after the toner image is transferred is cleaned by the cleaning blade 504.

  The cleaning blade 504 is configured to contact and separate from the outer peripheral surface of the intermediate transfer belt 501 at a predetermined timing by a cleaning member separation / contact mechanism (not shown).

  A toner seal member 502 that contacts and separates from the outer peripheral surface of the intermediate transfer belt 501 is provided on the upstream side of the cleaning blade 504 with respect to the direction in which the intermediate transfer belt 501 moves. The toner seal member 502 receives the toner dropped from the cleaning blade 504 when the intermediate transfer belt 501 is cleaned, and prevents the toner from scattering on the transfer path of the transfer paper P. The toner seal member 502 is brought into contact with and separated from the outer peripheral surface of the intermediate transfer belt 501 together with the cleaning blade 504 by a cleaning member separating and contacting mechanism.

  The lubricant 506 scraped by the lubricant application brush 505 is applied to the outer peripheral surface of the intermediate transfer belt 501 thus cleaned.

  The lubricant 506 is made of, for example, a solid body such as zinc stearate, and is installed so as to be in contact with the lubricant application brush 505.

  Further, the electric charge remaining on the outer peripheral surface of the intermediate transfer belt 501 is removed by a neutralizing bias applied by a neutralizing brush (not shown) in contact with the outer peripheral surface of the intermediate transfer belt 501. Here, the lubricant application brush 505 and the static elimination brush are configured to be brought into contact with and separated from the outer peripheral surface of the intermediate transfer belt 501 at a predetermined timing by a contact and separation mechanism (not shown).

  Here, at the time of repeat copying, the photosensitive drum 200 forms the second K toner image at a predetermined timing after forming the first Y toner image. Further, after the first toner image is transferred to the transfer paper P, the second K toner image is transferred to the intermediate transfer belt 501. Thereafter, an image is formed by the same operation as the first sheet.

  In the three-color copy mode and the two-color copy mode, an image is formed by the same operation as described above for the designated color and number of times.

  In the case of the single color copy mode, only the predetermined color developer of the revolver developing unit 230 is set at the developing position until the predetermined number of sheets is completed, and the cleaning blade 504 is brought into contact with the intermediate transfer belt 501. An image is formed as it is.

  3, another example of the image forming apparatus includes photosensitive drums 21K, 21Y, 21M, and 21C that form toner images of black (K), yellow (Y), magenta (M), and cyan (C). A four-drum digital color printer is shown.

  The printer body 10 includes an image writing unit 12, an image forming unit 13, and a paper feeding unit 14 for forming a color image by an electrophotographic method. Based on the image data, an image processing unit (not shown) performs image processing to convert the image signal of each color, and transmits the image signal to the image writing unit 12. The image writing unit 12 is a laser scanning optical system including a laser light source, a deflector such as a rotating polygon mirror, a scanning imaging optical system, and a mirror group, and has four writing optical paths corresponding to the image signals of each color. The photoreceptors 21K, 21M, 21Y, and 21C provided for each color of the forming unit 13 are exposed according to the image signal of each color.

  The image forming unit 13 includes photoconductors 21K, 21M, 21Y, and 21C.

  As the photoconductor, an OPC photoconductor is usually used.

  Around the photoreceptors 21K, 21M, 21Y, and 21C, there are a charging device, an image writing unit 12, developing devices 20K, 20M, 20Y, and 20C, primary transfer bias rollers 23K, 23M, 23Y, and 23C, and a cleaning device (not shown). ) And a static eliminator (not shown).

  The developing devices 20K, 20M, 20Y, and 20C use a two-component magnetic brush developing method.

  The intermediate transfer belt 22 (see FIG. 1) is interposed between the photoreceptors 21K, 21M, 21Y, and 21C and the primary transfer bias rollers 23K, 23M, 23Y, and 23C, and is formed on the photoreceptor of each color. The toner images of each color are sequentially transferred and superimposed.

  On the other hand, the transfer paper P is fed from the paper feed unit 14 and then carried on the transfer conveyance belt 50 via the registration rollers 16. The toner image transferred onto the intermediate transfer belt 22 is transferred onto the transfer paper P by the secondary transfer bias roller 60 when the intermediate transfer belt 22 and the transfer conveyance belt 50 come into contact with each other. The transfer paper P onto which the toner image has been transferred is conveyed to the fixing device 15 by the transfer conveying belt 50, and after the toner image is fixed by the fixing device 15, it is discharged from the printer main body 10.

  The toner remaining on the intermediate transfer belt 22 is cleaned by the cleaning member 25.

  A lubricant application device 27 is installed on the downstream side of the cleaning member 25 with respect to the direction in which the intermediate transfer belt 22 moves.

  The lubricant application device 27 includes a solid lubricant and a conductive brush that rubs against the intermediate transfer belt 22 to apply the solid lubricant.

  The conductive brush always contacts the intermediate transfer belt 22 and applies a solid lubricant to the intermediate transfer belt 22.

  Since the solid lubricant improves the cleaning property of the intermediate transfer belt 22 and prevents the occurrence of filming, the durability of the intermediate transfer belt 22 can be improved.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the examples. In addition, a part is a mass part.

[Example 1]
<Preparation of coating solution for substrate>
Using a bead mill, 15 parts of acidic carbon black Special Black 4 (manufactured by Orion Engineered Carbons) having a pH of 3 and a volatile content of 14% is dispersed in 85 parts of N-methyl-2-pyrrolidone to disperse the acidic carbon black. A liquid was obtained.

  U-varnish A (manufactured by Ube Industries) and U-varnish S (manufactured by Ube Industries) as a polyimide varnish mainly composed of polyamic acid, which is a polyimide resin precursor, were mixed at a solid content ratio of 6: 4. Next, the dispersion of acidic carbon black was added so that the mass ratio of acidic carbon black to polyamic acid was 0.17, and then stirred and mixed to obtain a coating solution for a substrate.

<Formation of substrate>
Coating on a substrate so that it is uniformly cast using a dispenser while rotating a metal cylindrical mold having an outer diameter of 375 mm, a length of 360 mm, and an outer surface roughened by blasting at 50 rpm. The liquid was applied. When the coating film spreads evenly, the number of rotations was increased to 100 rpm, and then introduced into a hot-air circulating dryer, and the temperature was gradually raised to 110 ° C. and heated for 60 minutes. Furthermore, after heating up to 200 degreeC and heating for 20 minutes, rotation was stopped, it cooled gradually, and it took out from the hot air circulation dryer. Next, the cylindrical mold on which the dried coating film is formed is introduced into a heating furnace (firing furnace), heated up to 360 ° C. in steps and heated (firing) for 60 minutes, then cooled, A substrate containing 60 μm polyimide was formed.

<Preparation of coating solution for surface layer>
12 parts of acidic carbon black MA100 (manufactured by Mitsubishi Chemical Corporation) having a pH of 3.5 and a volatile content of 1.5% were dispersed in 88 parts of cyclohexanone to obtain a dispersion of acidic carbon black.

  Modified polyrotaxane-graft-polycaprolactone (CAS No. 928045-45-8) Celm superpolymer SH3400P (manufactured by Advanced Soft Materials) was dissolved in cyclohexanone to obtain a solution of modified polyrotaxane-graft-polycaprolactone.

  Here, the modified polyrotaxane-graft-polycaprolactone is a polyrotaxane graft-modified with polycaprolactone, and the polyrotaxane has a linear molecule of polyethylene glycol, a blocking group of adamantyl group, and a cyclic molecule of hydroxylpropyl A cyclodextrin having a group.

  In a solution of modified polyrotaxane-graft-polycaprolactone, hexamethylene diisocyanate polyisocyanate (block isocyanate) Duranate TPA-B80E (manufactured by Asahi Kasei Chemical Co., Ltd.) so that the molar ratio of isocyanate groups to hydroxyl groups is 1.05. added. Next, a dispersion of acidic carbon black was added so that the mass ratio of acidic carbon black to the total solid content was 0.1, to obtain a surface layer coating solution.

<Formation of surface layer>
While rotating the cylindrical mold on which the substrate containing polyimide was formed at 50 rpm, the surface layer coating solution was continuously discharged from the nozzle, moved in the axial direction of the cylindrical mold, and applied spirally. Next, while rotating the cylindrical mold coated with the surface layer coating liquid at 100 rpm, it was introduced into a hot air circulating dryer, heated to 150 ° C. at a temperature rising rate of 3 ° C./min, and heated for 30 minutes, A surface layer having a thickness of 100 μm was formed. Further, the substrate on which the surface layer was formed was removed from the cylindrical type to obtain an intermediate transfer belt. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10.degree. C. and 15% RH of 11.3 [Log (.OMEGA ./. Quadrature.)], And a common logarithm of surface resistivity at 27.degree. C. and 80% RH of 10. 9 [Log (Ω / □)].

  The thickness of the substrate and the surface layer is an average value of the thicknesses at 10 locations measured by observing the cross section of the intermediate transfer belt using a scanning electron microscope (SEM).

  In addition, the surface resistivity of the intermediate transfer member was measured at 10 locations that were read 10 seconds after applying a voltage of 500 V to the side on which the surface layer was formed using Hiresta MCP-HT450 (manufactured by Mitsubishi Chemical Analytech). It is an average value of surface resistivity.

[Example 2]
When preparing the surface coating solution, Special Black 4 (made by Orion Engineered Carbons) having a pH of 3 and a volatile content of 14% was used as the acidic carbon black, and the mass ratio of the acidic carbon black to the total solid content was 0. An intermediate transfer belt was obtained in the same manner as in Example 1 except that it was changed to .16. The intermediate transfer belt has a common logarithmic value of surface resistivity of 11.4 [Log (Ω / □)] at 10 ° C. and 15% RH, and a common logarithm of surface resistivity of 10 ° C. and 80% RH of 10. 0.5 [Log (Ω / □)].

[Example 3]
When preparing the coating solution for the surface layer, Color Black FW2 (manufactured by Orion Engineered Carbons Co., Ltd.) having a pH of 2.5 and a volatile content of 16.5% was used as acidic carbon black. An intermediate transfer belt was obtained in the same manner as in Example 1 except that the black mass ratio was changed to 0.19. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10 ° C. and 15% RH of 11.6 [Log (Ω / □)], and a common logarithmic value of surface resistivity at 27 ° C. and 80% RH of 10 3 [Log (Ω / □)].

[Example 4]
When preparing the surface layer coating solution, Color Black FW200 (manufactured by Orion Engineered Carbons Co., Ltd.) having a pH of 2.5 and a volatile content of 20% was used as acidic carbon black. An intermediate transfer belt was obtained in the same manner as in Example 1 except that the mass ratio was changed to 0.25. The intermediate transfer belt has a common logarithmic value of the surface resistivity at 10 ° C. and 15% RH of 11.8 [Log (Ω / □)], and a common logarithm of the surface resistivity at 27 ° C. and 80% RH of 9. 9 [Log (Ω / □)].

[Example 5]
An intermediate transfer belt was obtained in the same manner as in Example 1 except that the thickness of the surface layer was changed to 20 μm. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10.degree. C. and 15% RH of 11.3 [Log (.OMEGA ./. Quadrature.)], And a common logarithm of surface resistivity at 27.degree. C. and 80% RH of 10. 9 [Log (Ω / □)].

[Example 6]
An intermediate transfer belt was obtained in the same manner as in Example 1 except that the thickness of the surface layer was changed to 350 μm. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10.degree. C. and 15% RH of 11.3 [Log (.OMEGA ./. Quadrature.)], And a common logarithm of surface resistivity at 27.degree. C. and 80% RH of 10. 9 [Log (Ω / □)].

[Example 7]
<Preparation of coating solution for substrate>
Using a bead mill, acidic carbon black MA77 (manufactured by Mitsubishi Chemical Corporation) was dispersed in N-methyl-2-pyrrolidone to obtain a dispersion of acidic carbon black.

  A dispersion of acidic carbon black is added to Viromax HR-16NN (manufactured by Toyobo Co., Ltd.) as a polyamideimide varnish mainly composed of polyamideimide so that the mass ratio of acidic carbon black to polyamideimide is 0.24. Then, the mixture was stirred and mixed to obtain a coating solution for a substrate.

<Formation of substrate>
Coating on a substrate so that it is uniformly cast using a dispenser while rotating a metal cylindrical mold having an outer diameter of 375 mm, a length of 360 mm, and an outer surface roughened by blasting at 50 rpm. The liquid was applied. When the coating film spreads evenly, the number of rotations was increased to 100 rpm, and then introduced into a hot-air circulating dryer, and the temperature was gradually raised to 110 ° C. and heated for 60 minutes. Furthermore, after heating up to 200 degreeC and heating for 20 minutes, rotation was stopped, it cooled gradually, and it took out from the hot air circulation dryer. Next, the cylindrical mold with the dried coating film formed is introduced into a heating furnace (firing furnace), heated up to 250 ° C. stepwise and heated (firing) for 60 minutes, then cooled, A substrate containing 60 μm polyamideimide was formed.

<Formation of surface layer>
An intermediate transfer belt was obtained in the same manner as in Example 1 except that a substrate containing polyamideimide was used instead of the cylindrical type on which a substrate containing polyimide was formed. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10.degree. C. and 15% RH of 11.3 [Log (.OMEGA ./. Quadrature.)], And a common logarithm of surface resistivity at 27.degree. C. and 80% RH of 10. 8 [Log (Ω / □)].

[Comparative Example 1]
An intermediate transfer belt was obtained in the same manner as in Example 1 except that acidic carbon black was not added when preparing the surface layer coating solution. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10 ° C. and 15% RH of 12.5 [Log (Ω / □)], and a common logarithmic value of surface resistivity at 27 ° C. and 80% RH of 9. 0.1 [Log (Ω / □)].

[Comparative Example 2]
When preparing the coating solution for the surface layer, instead of acidic carbon black, basic carbon black (Ketjen Black) EC300J (made by Lion Chemical Co., Ltd.) having a pH of 9.0 and a volatile content of 0.5% was used. An intermediate transfer belt was obtained in the same manner as in Example 1 except that the mass ratio of basic carbon black to the total solid content was 0.02. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10 ° C. and 15% RH of 12.5 [Log (Ω / □)], and a common logarithmic value of surface resistivity at 27 ° C. and 80% RH of 9. 2 [Log (Ω / □)].

[Comparative Example 3]
When preparing the coating solution for the surface layer, neutral carbon black # 3350B (manufactured by Mitsubishi Chemical Corporation) having a pH of 7.0 and a volatile content of 1.0% was used instead of acidic carbon black, and the total solid content was An intermediate transfer belt was obtained in the same manner as in Example 1 except that the mass ratio of neutral carbon black was 0.12. The intermediate transfer belt has a common logarithmic value of surface resistivity at 10.degree. C. and 15% RH of 12.1 [Log (.OMEGA ./. Quadrature.)], And a common logarithm of surface resistivity at 27.degree. C. and 80% RH of 9. 8 [Log (Ω / □)].

  Table 1 shows the characteristics of the intermediate transfer belt.

次に、中間転写体の画像濃度のムラ及び環境による画像濃度の変化を評価した。

Next, the unevenness of the image density of the intermediate transfer member and the change in the image density due to the environment were evaluated.

[Image density unevenness]
The intermediate transfer belt was mounted on an imagio MPC7501 (manufactured by Ricoh) to form an image, and image density unevenness was evaluated. Specifically, after outputting ten cyan and magenta solid images at 10 ° C., 15% RH and 27 ° C., 80% RH, the worst sample was visually observed. As the paper, FC Japanese paper type <ripple wave> (manufactured by Ricoh) was used. Here, the FC Japanese paper type <ripple wave> (manufactured by Ricoh) is a rough paper having a concavo-convex pattern in a Japanese paper style. It should be noted that the case where the unevenness of the image density cannot be confirmed is ○, the partial unevenness of the image density can be confirmed, but the case where it is a usable level is Δ, the case where the unevenness of the image density is large and the level is not usable. Judged as x.

[Change in image density due to temperature and humidity environment]
The intermediate transfer belt was mounted on the image forming apparatus of FIG. 3 to form an image, and the change in image density due to the temperature and humidity environment was evaluated. Specifically, after forming a blue solid image at 10 ° C., 15% RH and 27 ° C., 80% RH, image density ID was measured using X-rite (manufactured by X-Rite). As the paper, FC Japanese paper type <ripple wave> (manufactured by Ricoh) was used. Note that the case where the difference in image density due to the temperature and humidity environment was less than 0.2 was judged as ◯, the case where it was 0.2 or more and less than 0.5 was judged as Δ, and the case where it was 0.5 or more was judged as ×.

  Table 2 shows the evaluation results of the image density variation of the intermediate transfer body and the change in the image density due to the temperature and humidity environment.

表２から、実施例１〜７の中間転写ベルトは、粗い紙に画像を形成しても、画像濃度のムラ及び温湿度環境による画像濃度の変化が小さいことがわかる。

From Table 2, it can be seen that the intermediate transfer belts of Examples 1 to 7 have small image density variations and small changes in image density due to the temperature and humidity environment even when an image is formed on rough paper.

  In contrast, the intermediate transfer belt of Comparative Example 1 has a surface layer that does not contain acidic carbon black. Therefore, when an image is formed on rough paper, the change in image density due to the temperature and humidity environment is large.

  Further, since the intermediate transfer belts of Comparative Examples 2 and 3 are formed with a surface layer containing basic carbon black and neutral carbon black instead of acidic carbon black, when an image is formed on rough paper, the image density is reduced. The change in image density due to unevenness and temperature / humidity environment is large.

11 Substrate 12 Surface layer 22,501 Intermediate transfer belt

JP 2013-29632 A

Claims (6)

A surface layer is formed on the substrate,
The surface layer includes polyrotaxane and acidic carbon black,
Difference between the common logarithm of the surface resistivity on the side where the surface layer is formed at 10 ° C. and 15% RH and the common logarithm of the surface resistivity on the side where the surface layer is formed at 27 ° C. and 80% RH The intermediate transfer belt is characterized in that is 2 [Log (Ω / □)] or less.   The intermediate transfer belt according to claim 1, wherein the acidic carbon black has a volatile content of 15% or less.   The intermediate transfer belt according to claim 1, wherein the surface layer has a thickness of 30 μm to 300 μm.   The intermediate transfer belt according to any one of claims 1 to 3, wherein the substrate includes polyimide or polyamideimide.   The intermediate transfer belt according to any one of claims 1 to 4, wherein the intermediate transfer belt is a seamless belt. A photoreceptor,
The intermediate transfer member according to any one of claims 1 to 5,
Charging means for charging the photoreceptor;
Exposure means for exposing the charged photoreceptor to form an electrostatic latent image; and
Developing means for developing the electrostatic latent image formed on the photoreceptor with toner to form a toner image;
First transfer means for transferring a toner image formed on the photosensitive member to the intermediate transfer member;
An image forming apparatus comprising: a second transfer unit that transfers a toner image transferred to the intermediate transfer member to a recording medium.

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